In electronic design, many circuits, components and systems must be tested and data from such tests must be documented, stored and later retrieved for comparison with other data or analyzed by computer means. Conventional data acquisition by digitizing the electrical signals allows data to be stored in computer readable form; however, any sample rate selected for capture limits the range of data to (sample interval) * (record length). Any information outside the selected time window cannot be reconstructed at a later time. Because of this constraint, careful planning of the test setup is required. Alternatively, data may be captured from multiple test setups to cover a wider time range.
These test setups are cumbersome yet cannot guarantee sufficient data for accurate comparison or processing at a future date. Many attempts, such as delayed sweep, delayed trigger, logic trigger and increasing record length have been made to minimize this problem. Increasing data size allows extension of the time window, but always a memory size limitation remains, thereby limiting the time window.
Conventional data capture can cause further difficulties if the data is to be compared with data from computer simulation of electronic circuits. Such simulation can readily simulate electronic circuit behavior over a time range from picoseconds to seconds. For example, if a conventional data acquisition system were to be used to capture data over a one second time interval with time resolution of 10 picoseconds, 100 billion data samples would be required. This, obviously, would require too much data memory, and therefore one would be restricted to either limited time resolution or a limited time window or both. Also, since typical record lengths are 1,000 to 10,000 samples, multiple data acquisition cycles and multiple records are required to capture even a moderate time window with fine time resolution. It would be desirable to provide a data acquisition system that captures data over wide time intervals with fine time resolution.